1. Field of the Invention
The present invention relates generally to the field of drilling and servicing subsurface wells, and more specifically to an apparatus and method for converting the kinetic energy of the flow of fluid past a device such as a turbine into rotational kinetic energy and for applying the rotational kinetic energy of the device to rotate a steerable motor or other downhole tool relative to a point of reference. In more detail, the present invention relates to an orienter for use in directional drilling, fishing operations, well intervention, or for re-entry of multilateral wells, particularly on coiled tubing (CT) or small diameter drill pipe. In one embodiment, the invention includes means for using mud flow through the tool for generating electricity for powering a motor for rotating the downhole tool, and a method of orienting a downhole tool with electricity generated downhole.
2. The Related Art
A directional or deviated borehole is typically drilled using a positive displacement mud motor, a bent housing, and a bit that are suspended on drill pipe that extends downwardly into the borehole from the surface. The drill pipe is rotated at the surface to orient the bent housing to control the tool face angle and thus the azimuth at which the borehole is drilled. The motor is generally powered by pumping a weighted drilling fluid (mud) down the drill string and through the motor.
Coiled tubing (CT) can be run into a borehole that is under pressure through blowout preventers using a tubing injector and, with a drilling motor mounted on or near the end of the tubing, is particularly useful in some circumstances for drilling deviated boreholes and for accommodating multiphase drilling fluids. However, CT cannot be rotated at the surface to achieve directional steering of a drilling motor and bent housing. For that reason, the bottom hole assembly (BHA) generally includes an orienter that is operated by pulsing the drilling fluid by cycling the pumps on and off, each change causing the orienter to rotate by an incremental amount to orient the bent housing relative to the direction of the CT to achieve a desired tool face angle. Other systems control the orienter by running hydraulic and/or electric umbilicals or cables from the surface for both power and two-way data telemetry between the surface and the downhole tools. Such systems have the advantage of higher power and insensitivity to multiphase drilling fluids. In some systems known in the art, the electric cable provides electric power to an electric motor for controlling the tool face angle and to continuously rotate the bent housing when desired for straight ahead drilling. Examples of such tools include those described in U.S. Pat. No. 5,894,896 (hydraulic), U.S. Pat. No. 5,669,457 (hydraulic), U.S. Pat. No. 5,215,151 (mud pulse), U.S. Pat. No. 5,311,952 (mud pulse), U.S. Pat. No. 5,735,357 (mud pulse), and International Application No. PCT/EP95/05163 (WO 96/19635) (electric cable).
However, such systems are characterized by a number of disadvantages and limitations that compromise their utility. For instance, the fluid inertia time delay of mud pulse systems make orienting the bent housing a time consuming process. Further, the flow rate must be reduced substantially and the bit must be xe2x80x9coff bottomxe2x80x9d during orienting, necessarily interrupting drilling operations. Further, the use of multiphase or gaseous drilling fluid hampers and significantly slows the operation of these pressure operated orienters. Also, most such systems are capable of rotation in only one direction by a set increment such that it is necessary to rotate 345xc2x0 counterclockwise if it is desired to rotate, for instance, 15xc2x0 clockwise. Straight ahead drilling requires a series of 180xc2x0 arcs for certain mechanical tools, or removing the bend from the BHA (requiring a trip to the surface).
Adding umbilicals to the system increases available power and torque, but necessarily complicates deployment, requires increased surface pump pressure to achieve the necessary flow rates with which to drill reducing coil life, and impacts the process of cementing and completing the well after drilling.
There is, therefore, a need for an apparatus and method for orienting a downhole tool that overcomes these limitations. It is therefore a general object of the present invention to provide an orienter with increased power and torque delivery downhole that produces mechanical or electrical power with a downhole turbine or other device that is rotated by the flow of drilling mud or other fluid.
A further object of the present invention is to provide an orienter that converts the hydraulic energy of fluid pumped in a borehole to power for directly rotating a downhole tool.
Another object of the invention is to convert the whole or a part of the fluid energy into electrical energy for powering an electric motor, electric clutch, and/or an electronic sensor and control package.
Another object of the present invention is to provide a downhole orienter that is operated while drilling, thereby reducing down time.
Another object of the present invention is to provide a downhole orienter that does not have xe2x80x9cumbilicalsxe2x80x9d to the surface but is insensitive to the presence of multiphase drilling fluids.
It is also an object of the present invention to provide an orienter that is utilized for quickly and reliably orienting a downhole tool to a desired azimuth in a single step.
It is also an object of the present invention to provide an orienter capable of continuous rotation.
It is also an object of the present invention to provide an orienter that comprises a closed loop system with a steering tool for continuously orienting to an absolute heading while drilling and maintaining a specified inclination and/or build-up rate.
It is also an object of the present invention to provide an orienter for use in downhole operations other than drilling, such as well intervention, orienting a whipstock or multilateral re-entry tool, for setting a packer, kickpad or other diverter, or for fishing operations.
Other objects, and the advantages, of the method and apparatus of the present invention will be made clear to those skilled in the art by the following description of the presently preferred embodiments thereof.
These objects are achieved by providing an improved orienter for a downhole tool that generates rotational kinetic energy from the flow of fluid through the orienter for rotating the tool relative to a point of reference. In a preferred embodiment, the orienter selectively rotates the downhole tool in response to an input signal.
In another aspect, the present invention is directed to an apparatus for orienting a tool in a borehole comprising a device for converting fluid flow into rotational kinetic energy, means for applying the rotational kinetic energy of the device to change the orientation of a tool in the borehole, and means for communicating a desired change in the orientation of the tool to the kinetic energy applying means. In a preferred embodiment, the direction communicating means is responsive to one or more of a signal from the surface, a signal from a direction and inclination package, or a signal from an MWD/LWD tool. In one preferred embodiment, the rotational kinetic energy applying means includes a gear train that converts a higher velocity, lower torque input into a lower velocity, higher torque output. In a second preferred embodiment, the rotational kinetic energy applying means includes an alternator for generating electrical power from the rotational kinetic energy of the device and an electric motor powered by the electricity generated by the alternator.
In another aspect, the present invention is directed to an orienter for a downhole tool comprising a device for converting fluid flow through the device into rotational kinetic energy, an alternator operably connected to the device for converting the rotational kinetic energy produced by the device into electricity, and either a motor powered by the electricity produced by the alternator or an electrically operated clutch operably connected to the alternator. In one embodiment, control circuitry that is also powered by the electricity produced by the alternator is also provided for selectively operating the motor for orienting a downhole tool. The device may include means reactive to input signals from the surface for selectively orienting the downhole tool. The signal sensing means may be reactive to, for instance, reciprocating movement of the tubular string or changes in the pressure or fluid flow past the device, or in the case of the above-described control circuitry, the control circuitry may sense other input signals such as a telemetered signals from the surface, or signals from a direction and inclination package, or an MWD/LWD tool.
Also provided is a method for orienting a tool in a borehole relative to a point of reference. In a preferred embodiment, the method of the present invention comprises the steps of pumping a fluid through a tubular string in a borehole, generating rotational power from the hydraulic energy of the pumped fluid, and utilizing the rotational power generated from the hydraulic energy of the pumped fluid to selectively rotate a tool relative to a point of reference. The rotational power generated from the hydraulic energy of the pumped fluid is mechanical power or electric power, the former being utilized directly to rotate the tool and the latter being utilized either to power an electric motor that rotates the tool or to actuate a clutch that operably connects the alternator to the tool.